A negative pressure respirator mask typically is leak tested by covering the air inlet and inhaling until the mask is slightly collapsed. A positive pressure respirator is similarly leak tested by covering the air outlet and exhaling until the mask bulges. These tests of time holding pressure are both subjective and static in that the quality of the mask seal (and other potential leak paths including valves) as a function of time is not measured. Quantitative testing estimates fit (the inverse of leakage) for a specific model of mask and individual wearer. While of considerable advantage in mask selection and design, the usage of aerosol flow, and other conventional techniques, renders quantitative leak testing techniques incompatible with in situ field use.
Thus, there exists a need for an in situ apparatus and process for testing a respiratory mask seal during actual usage. Such an apparatus and process could continuously monitor fit (leakage) and be used to alert the wearer to mask failure.